The regular M4A1 is always equipped with a foregrip and a unique Reflex Sight, while the Grenadier variant is fitted with its grenade launcher and a Holographic Sight. All variants are equipped with the AN/PEQ-2A.

The M4A1 SOPMOD with iron sights that is found in "Ultimatum" (via "give all" console command) has the correct pick-up icon for the default M4A1 SOPMOD. Like the G36C, the M4A1 is not available without a Red Dot Sight or a substitute of it in the campaign, unless the player spawns a different version via the console in "Ultimatum", "All In", or "No Fighting In The War Room".

Known instead as the M4 Carbine, is unlocked at level 10. It can be modified with an M203, Red Dot Sight, Silencer, or ACOG Scope after having completed the respective marksman challenges. The M4 Carbine is an excellent weapon in the right hands, with moderate damage and fairly low recoil. However, the M4 Carbine has fast, large idle sway making it more difficult to aim properly at long range. The M4 Carbine shares ammunition with the M16A4 and the G36C. The M4 Carbine is one of the most versatile weapons in online multiplayer on all platforms, due to its low unlock level and good stats.

The M4 Carbine deals 20-30 damage, killing in 4-5 shots. Stopping Power increases damage to 28-42 damage, killing in 3-4 shots. Head shots come with a 1.4x multiplier typical for most assault rifles, usually allowing the M4 Carbine to kill in one fewer bullet depending on range. While it is a lower per-shot damage assault rifle on par with the G36C, the M4 Carbine's low damage output is mitigated by its high rate of fire and very low recoil (with a recoil pattern of 40 on each side, 50 upwards, and 30 downwards), allowing for accurate automatic fire at both short and medium ranges, or even burst firing at long ranges.

The M4 Carbine is ideal in both close quarters and mid-range combat due to its high rate of fire, decent hipfire accuracy, and low recoil. Steady Aim makes the M4 Carbine even better in close quarters. While the M4 Carbine benefits less from Stopping Power than other assault rifles due to the rapid rate of fire, it still improves further upon the weapon's versatility, making it more deadly at any range. The M4 Carbine has good reload speeds and a fast rate of fire, making ammo consumption rapid. Bandolier aids the player's longevity in combat by offering a large supply of starting ammunition. The M4 Carbine is an excellent stealth weapon due to its affinity for closer range combat, so perks like Dead Silence and UAV Jammer can be useful with it.

The M4A1 returns in Call of Duty: Modern Warfare 2, this time with a tan finish like many other weapons in the game. Unlike its Call of Duty 4: Modern Warfare counterpart, the Call of Duty: Modern Warfare 2 version does not have the carrying handle and iron sights, instead having a Picatinny rail and a backup iron sights mounted. Aside from the appearance and sounds, however, the weapon is completely unchanged from Call of Duty 4.

The plain M4A1 is the first weapon used by PFC Allen in "S.S.D.D.", and can be taken from dead allies later in the game. This is also the only campaign variant without an M203.

The most common variants are the four "Grenadier" variants with different optics. The ironsight "M4A1 Grenadier" is commonly used by allies, and is one of Allen's second starting weapon in "No Russian". It is also acquired at the start of "Whiskey Hotel" along with an M9, unless the player plays it immediately after "Second Sun", in which case he retains his weapons from that level. It is also found next to some dead Rangers and ammunition crates in the aforementioned levels and "Of Their Own Accord".

The "M4A1 Grenadier w/ Red Dot Sight" is less commonly used by Task Force 141 members, most notably by Roach. One is given to him after planting the C4 in "The Only Easy Day... Was Yesterday". It seems to be his M4A1 SOPMOD with the Suppressor detached. The same variant is used by Soap after Roach detonates the C4. In "The Gulag" Roach's second starting weapon is a unique Arctic Camouflage version of it, which is the only camouflaged M4A1 in the Modern Warfare 2 campaign. This variant also appears to have an invisible infrared laser sight under the barrel, acting identically to the one in Call of Duty 4, visible only with nightvision. The same weapon is later found in the armory in "Loose Ends", again, with the standard tan and black finish. This variant is also rarely used by Task Force 141 NPCs in most levels where they are encountered. Note that the Red Dot Sight on this variant has the zoom level of an ACOG scope.

The "M4A1 Grenadier w/ Holographic" is less commonly used by Rangers and Task Force 141 NPCs. It is the starting weapon of Pvt. Ramirez in "Of Their Own Accord". Another one is automatically taken after using the Javelin in the "crow's nest". After the helicopter crash another one is given to him by Wade, but most players abandon it after the EMP in favor of the iron sight variant.

The "M4A1 Grenadier w/ ACOG Sight" is less commonly used by Task Force 141 NPCs. In "The Gulag", Soap uses one to launch a flare from its M203 for the chopper to drop the SPIE rig. Several are also found on the upper floors of the building in "Of Their Own Accord", before boarding the Black Hawk.

Before planting the C4 in "The Only Easy Day... Was Yesterday", Roach uses a suppressed variant of the "M4A1 Grenadier w/ Red Dot Sight" called the "M4A1 SOPMOD". It uses the same attachments as in Call of Duty 4, with their Modern Warfare 2 appearances. Its Red Dot Sight has the zoom level of a Holographic Sight.

The "M4A1 Suppressed" is seen used by friendly NPCs during the stealth "The Only Easy Day... Was Yesterday". It can only be obtained by the player in the Museum. This M4A1 has a unique pickup icon, which appears to be the unused M4A1 with a silencer and the singleplayer Red Dot Sight from Call of Duty 4: Modern Warfare, a theory reinforced by the name "M4A1 Suppressed", which they share.

The M4A1 is available at level 4 as a default weapon when Create-a-Class is unlocked.

In terms of damage per bullet, it is amongst the weakest of Assault Rifles, tied with the ACR and the F2000. The M4A1 will deal four to five shot kills if not using Stopping Power; Stopping Power makes one less bullet required to kill an enemy in all circumstances. Its low damage is offset by an impressive rate of fire, although not to the degree of the F2000's. It will fire at an impressive 857 RPM.

The M4A1 is a highly accurate weapon, as the recoil is very low, but the iron sights can be somewhat obstructive due to the large frame. Optical attachments can be used if a player finds that the sights disruptive in their aiming ability.

Handling traits of the gun are relatively straightforward: the hip-fire spread is moderately sized, the player will move at the Assault Rifle default speed, and the reload times are the fastest in its class, tied with the M16A4 and ACR. The M4A1 has a 30 round magazine by default.

The usual assortment of attachments are available for the M4A1. The Red Dot Sight and the Holographic Sight are common choices on the weapon to replace the somewhat obstructive iron sights. The ACOG Scope can be effective on the M4A1; however, the Thermal Scope will fare much more poorly in this regard.

If the player is comfortable with the iron sights, the Silencer or FMJ are very powerful choices to use on the M4A1. The Silencer will noticeably impact the player's effective range, but it can be well-worth the cost of staying off the radar and having reduced muzzle flash. FMJ will allow a player to penetrate surfaces with relative ease, dealing much more damage to enemies hiding in buildings.

The underbarrel attachments are nothing special: the Grenade Launcher is always a solid choice if one wanted to make an Explosive Class, but the Shotgun is a poor choice on this weapon, as the M4A1 is already effective at close range. If the player desires another close-quarters backup, they should rely on their secondary.

Extended Mags increases the magazine size to 45 rounds, but in turn makes the supply limited between two magazines instead of three. This makes control of ammunition rather difficult if Scavenger is not in use, but lessening the need to reload is very beneficial, especially on a gluttonous weapon such as the M4A1.

Sleight of Hand Pro is a popular blue perk in order to compensate the common reloads the weapon will need, and speeding up the aim speed. Stopping Power Pro behaves as usual, and is recommended on the weapon due to the low damage. However, the weapon's high rate of fire somewhat compensates for the low damage, so the player may use a different red perk if they so desire. The yellow perk is all up to player preference, but should generally be used according to the player's strategy.

In conclusion, the M4A1 is an unusual threat in the battlefield, and is often overlooked due to low damage. However, a correct class setup can turn the tide of battles into the M4A1's favour. In terms of time-to-kill, it outclasses the ACR in all situations, but is subsequently outclassed by the F2000, especially at close range.

The M4A1 is a starting weapon in "The Pit" (M4A1 without any attachments), "Snatch and Grab" (M4A1 Grenadier w/ Red Dot Sight), "Breach and Clear" (Arctic camouflage M4A1 Grenadier w/ Red Dot Sight), "Estate Takedown" (M4A1 Grenadier w/ Holographic) and "Wetwork" (M4A1 Grenadier w/ Red Dot Sight). It an also be picked up in "Overwatch", "Estate Takedown" (M4A1 Grenadier w/ Red Dot Sight, found in the armory), "Wreckage" (M4A1 Grenadier, found many times in the level) and "Armor Piercing". All its variants are the same as in the Campaign.

The M4A1 in first person.

Aiming down the sights.

Reloading the M4A1. Note that the cartridges in the magazine are in 2D.

The M4A1 is featured in Call of Duty: Modern Warfare: Mobilized. This time, the standard M4A1 fires in three-round burst mode, whereas the Red Dot version is fully-automatic. The three-round burst M4 is almost a copy of the M16A4 found in Call of Duty 4: Modern Warfare. Notable differences are a slower rate of fire per burst but a smaller delay between them, as well as more compact iron sights.

The fully-automatic version with a Red Dot Sight has the same rate of fire but much more stopping power than the base M4A1. However, it has the second slowest rate of fire of all the assault rifles in the game. The weapon has a higher damage than the Call of Duty 4: Modern Warfare version, as it can perform a one-shot-kill if it is aimed at the chest at any range. Secondly, it has a higher rate of fire, and, lastly, like all the weapons of Call of Duty: Modern Warfare: Mobilized, it has almost no recoil when aiming down the sights.

In the campaign, the burst-firing M4A1 is exclusive to the level "Closing In", though it can be seen in use by allies in all the missions of the American campaign. It deals lower damage than the M4A1 Red Dot, but it still kills with one burst. The fully-automatic M4A1 Red Dot is a starting weapon in the last few missions of the American campaign, and in the middle of the Task Force 141 campaign. Since it has a high rate of fire, and only 120 reserved rounds to start with, it usually runs out of ammo before the end of the level.

In multiplayer, the three-round burst M4A1 is available by default, along with the MP5 and MP7. It is probably the least common weapon used in multiplayer, due to its lack of power, as it takes two bursts to kill, and low ammunition efficiency. Those who do use it usually discard it when the fully-automatic M4A1 Red Dot is unlocked, since it has much higher power and the same rate of fire as the M4A1, only without the delay between bursts.

The fully-automatic M4A1 Red Dot is unlocked for the Coalition faction, taking 50 kills to unlock. Due to its high rate of fire and low recoil, it is favored by many players. It is the most powerful, but slowest firing assault rifle in the game.

"In place of raw firepower, the M4A1 favors top handling and mobility. Minimal recoil keeps you on target through sustained fire, making up for the weapon's low damage output with consistent, accurate shots."

The M4A1 makes its return in Call of Duty: Modern Warfare 3. The M4A1 has a new look; a matte black finish, a custom charging handle assist, skeletonised stock, a different magazine, and slightly different iron sights. The M4A1 has a 30-round magazine. As in previous installments, a foregrip is mounted by default.

The M4A1 has the zoom of an ACOG Scope most of the time when aiming down the sights, regardless of which optic is attached, with the exception of the Hybrid Sight (in which case one will receive a normal zoom level when using the Red Dot Sight). Ironically, in "Down the Rabbit Hole", the M4A1 has an ACOG Scope attached, but it has the zoom of a Red Dot Sight.

The M4A1 is unlocked as soon as Create-A-Class is unlocked at Level 4. It has low to moderate recoil and a high rate of fire. The damage up close is high, requiring three hits to the body to kill, but the damage at range is very low, requiring five hits to the body, making the M4A1 more suited to close quarters. Possessing the fastest time to kill out of all the fully automatic assault rifles at close range, as well as the second fastest reload time, the M4A1 is a great choice for an aggressive playstyle. Stalker is useful in this regard, making strafing enemies at mid to close range easier and allowing one to quickly check corners while aiming down the sights. Scavenger is also very useful due to the M4A1's high rate of fire, as it will run out of ammo frequently, but Sleight of Hand ensures its user will never be caught dead while reloading. Due to the weapon's low recoil, the Kick proficiency is not required for short to medium range engagements, freeing up the proficiency slot for other useful options, such as Attachments or Stability. Players that have difficulty using the iron sights may find optical attachments useful; Extended Mag is also an effective option due to the M4A1's high rate of fire. Due to the significant difference between close-range and long-range damage, the Suppressor is not recommended on the M4A1, as this will negatively impact the weapon's performance more so than most other Assault Rifles.

The M4A1 is also featured in the game mode Money In The Denk. It is seen in the "Money" class, where it is equipped with a Red Dot Sight.

The M4A1 is available in Survival Mode by default and costs $3000. It is a solid weapon to start off with due to the good damage at close or medium range; it also has a good handling and high rate of fire. However, the M4A1 has low power at a distance and burns through ammunition quickly.

The US National Guard are often equipped with this. In the campaign, on various missions the player often starts off equipped with the M4, and later in the game the M4 can be picked up with various attachments. Unlike its Modern Warfare: Mobilized counterpart, the M4 is now fully-automatic by default, with a high rate of fire, penetration and average recoil.

The M4A1 was seen in a reveal poster, being held by a soldier, but was cut in the final game. A clearly unfinished menu icon is in the game files, lacking a complete model and is untextured. In the game the gun was named "M4."

The M4A1 returns in Call of Duty Online. It has a black finish, and unlike in previous installments it doesn't have a foregrip by default. Two other variants, the M4A1 Tech assault rifle and the M4LMG light machine gun, appear in the game as well.

The M4A1 appeared in the "Behind the Scenes Preview" video. Its appearance is that of the Call of Duty: Modern Warfare 3 M4A1. It is seen with a Grenade Launcher and Red Dot Sight at two points in the video. It still retains the foregrip as with previous Call of Duty games it appeared in. The Call of Duty: Modern Warfare 2 M4A1 is also seen in the same video in demonstrations of melee combat and the new mantle system. Either way, the weapon does not appear in the final game. However, if the player collects the Rorke file in "The Ghost Killer", there is an image that shows Rorke training with an M4A1 equipped with an M68 sight.

The lower receiver of the M4A1 has "BLUE4" written in tape; the M16A4 shares these markings. "BLUE4" is a reference to BluFor, the opposite of OpFor, which is applied to all NATO forces. It also says, "Property of U.S. Government, Caliber 5.56mm, M4A1 Carbine" over the magazine well.

When equipped with a Grenade Launcher, an unusuable leaf sight is attached onto the weapon's barrel.

The M4A1's serial number is "L141583"

Reloading the M4A1 Suppressed while there's still ammo in the magazine will give a different reload sound than the default weapon.

The number "04" can be seen on the rifle stock. It is also seen on the opposite side of the weapon, however flipped.

"PROPERTY OF U.S. GOVT. M4A1 CARBINE CAL 5.56MM S/N 90852390" can be seen engraved above the magazine. "RESTRICTED MILITARY/GOVERNMENT LAW ENFORCEMENT USE ONLY" can be seen engraved in the same location on the opposite side.

"FOR MILITARY/LAW ENFORCEMENT USE ONLY" can be seen engraved in between the fire selector and the bolt release. The characteristic "BLUE4" insignia is also drawn over the engraving.

"E523908" can be seen engraved underneath the rear iron sight.

Similar to the Call of Duty 4 variant, equipping a Grenade Launcher on the M4 Carbine results in an unusable leaf sight being attached to the barrel.